Research And Development Of Online Heating Process Equipment And Control System For Warm Rolling

In recent years,with the deepening of studies on hard-deformable metal materials such as magnesium alloys,it has been found that many difficult-to-deform metals forming processes with low plasticity and high deformation resistance are suitable for warm rolling.Before the emergence of the warm rolling mills,the off-line heating method was used to achieve the warm rolling process.The temperature of the rolled piece could not be guaranteed to be in a stable state.In addition,the roll contacted the heat conduction so that the temperature dropped drastically and the temperature of the rolled piece was in an uncontrollable state,so the on-line heating of the rolled piece and the roll are particularly important.Based on this demand,this paper develops an experimental device equipped with simultaneous on-line heating of rolled piece and rolls,and conducts in-depth research on its control system.The main jobs and innovations of this article are as follows:(1)The on-line heating process equipment for warm-rolling of hard-to-deform metal are researched and developed.Based on the high-precision hydraulic tension pilot cold-rolling mill,an on-line heating device for rolled piece was added,and left and right clamps and rolls were used as two electrodes,two transformers are respectively used to energize the two electrodes,and the rolled pieces clamped between the clamps and the rolls are heated on-line to realize on-line dynamic heating and tension rolling;another set is added.The roll heating system use the mineral oil of high temperature resistance as the medium to achieve on-line heating of the roll.(2)Resistance heating method was adopted to study on-line heating process equipment for rolled pieces.A contact-type special temperature measuring device for warm rolling was designed.Taking AZ31B magnesium alloy as an example,COMSOL FEM software was used to simulate and analyze the temperature rising related parameters of the resistance heating process.It was found that the higher the heating rate is,the more uniform the temperature of the rolled piece is;When the current density does not change,the thickness of the rolled piece has little effect on the resistance heating temperature;rolling width has no effect on the heating temperature of the rolled piece;the length of the rolled piece has a greater influence on the heating temperature,and with the increases of the rolled piece length,There is a significant increase in the soaking section.The above simulation results provide the basis and method to control the resistance heating process.(3)Three kinds of on-line heating methods of the roll were studied:heat transfer oil heating,induction heating and flame shock heating.The characteristics of different heating methods were analyzed.The heat transfer oil heating method has good temperature's uniformity and the energy storage time is relatively long.The induction heating method's heating speed is fast,but the uniformity of temperature is poor,the roll damage is large and the temperature retention is poor;the flame heating method is simple,but the temperature is not uniform enough,it is not suitable for light alloy materials such as magnesium alloys.After experimental verification,the heat transfer oil heating method is more suitable for the roll heating of experimental mills.The finite element software was used to simulate and analyze the heating method of heat transfer oil.The relationship between the inlet temperature of the thermal oil and the surface temperature of the roll was set,which provided the basis for the control of the heating process of the roll.(4)Taking AZ31B magnesium alloy as an example,the influence of the process parameters of the warm rolling process on the temperature of the rolling piece was analyzed by the finite element software DEFORM.The orthogonal experiment design method was used to analyze the effect of the five process parameters on the temperature of the rolled piece,and the outlet temperature model of the deformation zone of the rolled piece was established.Taking 86CrMoV7 roll material as an example,the relationship between roll temperature and various process parameters was analyzed,and the roll outlet temperature model was established.It provides a calculation method for the prediction of rolled piece's temperature and roll's temperature during warm rolling.(5)Combining the finite element simulation results of the temperature field in the deformation zone during the heating of the rolled piece,the heating of the roll and the warm rolling process,the temperature comprehensive control method in the warm rolling process is studied.The integrated control of the on-line heating process of the rolled piece is achieved through a combination of a feed forward controller and a feedback controller,and the heating process of the rolled piece is divided into two ways:static heating before rolling and dynamic heating during rolling,according to simulation results and the characteristics of controlling temperature,the control models of rolled piece temperature are given in two states.The Smith predictor is used to control the on-line heating process of the roll and control the oil temperature heating and heat preservation process so as to achieve simultaneous temperature rising and heat preservation of the roll temperature.(6)The research results are applied to the pilot warm rolling mill of the Baosteel Research Institute and the Chongqing Science and Technology Research Institute.The accuracy of the roll temperature control is ±10K,and the precision of the rolled piece temperature control is ±15K.Three groups of representative warm rolling experiments were completed on the warm rolling mill with a high-precision temperature control system:the relationship between surface quality and temperature of magnesium alloys,the relationship between edge cracking and temperature of magnesium alloys,Organization and performance experiments of magnesium alloys in warm rolling.The experimental results shows that the on-line heating and temperature control have an important influence on the forming quality of the magnesium alloy.The straight pull pilot warm rolling mill with high precision temperature control technology is researched and developed in this paper,it provides reliable processing equipment and technical support for the development and research in warm rolling process of various difficult-to-deform metal materials.